Most of the current Global Systems for Mobile communication (GSM) radio frequency (RF) transmitter architectures are based on the modulation loop architecture. While for receiver architectures, the trend is to adopt the direct conversion architecture, in order to achieve higher integration levels. Higher integration levels are achieved in direct conversion architectures due to not having to use intermediate frequency (IF) and image rejection filters.
With the move towards greater and greater integration levels, some RF semiconductor manufacturers are providing multi-band transceiver integrated circuits that integrate the receiver and most of the transmitter sections for use in hand-held or mobile applications. One example of such a multi-band transceiver IC is the UAA3535HL low power GSM/DCS/PCS multi-band transceiver, manufactured by Philips Semiconductors. This IC provides GSM, Digital Cellular communication Systems (DCS) and Personal Communication Services (PCS) support. Like the UAA3525HL multi-band transceiver IC, most current RF transceiver solutions currently available require two external dual band voltage-controlled oscillators (VCOs). One external multi-band VCO is required for the transmitter section and one external multi-band VCO is required for the receiver section. This of course not only adds to the cost of the design, but also increases the area needed to implement the design. A need thus exist in the art, for a solution to the abovementioned multi-VCO problem.